This isn't at all Quake-related (Warcraft III), but I am still modding (thankfully). It helps that my LAN game buddies enjoy playing this map with me. They're actually the main driving force to getting it done.
This is my Dragon Swarm map/mod. Waves of enemies come pouring in to your base, and you have to build towers to stop them from destroying your town hall.
The towers use command points (food) like normal units, and you can't build farms. Your food increases as you level up the Greater Command ability on your hero. This forces you to make do with less towers while you wait for your hero to level up. You also have to worry about upkeep, since you're mining gold for building and repairing towers.
Towers include Arrow, Glaive, Cannon, Lightning, Flame, etc. The flame towers napalm an area in a line, burning the ground for a while. I'm especially proud of these.

The lightning towers use chain lightning every 20 seconds or so. There's also some misc towers like the Spider Den (summons spiders) and Mine Tower (automatically mines the area around them).
This mod is nothing like the "Tower Defense" maps that Blizzard and others made. I hate those. The enemies just run right past and it's really not my style. In Dragon Swarm, enemies will attack your towers and base in overwhelming waves, and you've got to use your heroes to protect them or you're doomed.
I'll post the map itself sometime around the next stable release, for those who are interested.
When my computer inevitably explodes and kills me, my cat inherits everything I own. He may be the only one capable of continuing my work.